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Heavy crude oil (HCO) production, processing, and transportation forms several practical challenges to the oil and gas industry, due to its higher viscosity. Understanding the shear rheology of this HCO is highly important to tackle production and flow assurance. The environmental and economic viability of the conventional methods (thermal or dilution with organic solvents), force the industry to find an alternative. The present study was constructed to investigate the effect of eco-friendly ionic liquids (ILs) on the HCO's rheology, at high temperature and high pressure. Eight different alkyl ammonium ILs were screened for HCO's shear rheology at the temperatures of 25–100 °C and for pressures 0.1–10 MPa. The addition of ILs reduced the HCO's viscosity substantially from 25 to 33% from their original HCO viscosity. Also, it aids to reduce the yield stress to about 15–20% at all the studied experimental conditions. Furthermore, the viscoelastic property of the HCO was studied for both strain-sweep and frequency-sweep and noticed the ILs helps to increase HCO's loss modulus (G″) by reducing storage modulus (G′), it leads to the reduction of the crossover point around 25–32% than the standard HCO. Mean the ILs addition with HCO converts its solid-like nature into liquid-like material. Besides, the effect ILs chain length was also studied and found the ILs which has lengthier chain length shows better efficiency on the flow-ability. Finally, the microscopic investigation of the HCO sample was analyzed with and without ILs and witnessed that these ILs help to fragment the flocculated HCO into smaller fractions. These findings indicate that the ILs could be considered as the better alternative for efficient oil production, processing, and transportation.

High-belite cement (HBC) is increasingly used in hydraulic concrete, of which the frost resistance is an important index in cold climatic areas. In the present study, the mass loss, dynamic modulus, cube compressive strength, micro-morphology and pore characteristic parameters of HBC concrete and reference specimens were investigated under freezing and thawing, and their internal frost damages were quantified by micro-Vickers hardness and ultrasonic theory. Test results showed that the frost resistance of HBC concrete was similar to that of ordinary Portland cement (OPC) concrete under the same proportioning, and that their freeze–thaw failure was a continuous and asynchronous process of both surface-to-interior damage and overall deterioration caused by the test mechanism and specimen size. Service life of concrete could be calculated through the thickness of the damaged layer obtained by ultrasonic theory, and models of Vickers hardness distribution and compressive strength prediction based on equivalent Vickers hardness were proposed to evaluate the performance of frozen concrete with high accuracy. This potentially provides a better understanding of freeze–thaw damage and a reference for the popularisation and application of HBC concrete.

Regenerative medicine is used for tissue healing, replace missing organs and tissues which are affected by aging, disease, or trauma both structurally and functionally. Materials are the key component of regenerative medicine approaches because the material can imitate the native extracellular matrix of those tissues and improve both the physical behavior and the properties of new tissue. However, most of the available materials used for that purpose fail to provide adequate mechanical properties to replicate the behavior of the original tissue. Thus, most of these applications are still far from being enduring. This project aims to determine the multi-scale mechanical properties of some biopolymers with potential use in regenerative medicine. In this very first part, Dynamic Mechanical Analysis (DMA) was performed using shear mode on different type VII agarose-based biopolymers at room temperature during 10 min cycles at 1 Hz frequency. On one hand, samples of fibrine-agarose were tested, and on the other, different compositions of chitosan-agarose, while pure type VII agarose was used as control. Computed values for the storage and loss modulus and the small values for Tan delta ratio (tan δ) show that all materials become elastic, and they have a good capacity to dissipate energy per cycle of deformation. This fact means that all materials are suitable for being used as a scaffold for cell culture, a possible material for bioprinting applications and they could have potential use in regenerative medicine.

Dynamic mechanical analysis (DMA) is a technique that is used to study the viscoelastic behaviour of polymeric materials. 3D printing is one of the well-known applications of additive manufacturing techniques which has wide areas of application. In that, Fusion Deposition modelling (FDM) has very fine outcomes with better printing qualities to execute good products. In this research work, the 3D printed samples of pure ABS and PLA were examined under dynamic mechanical analysis to study the various temperature heat, absorbing, storing, and dissipating behaviour of these samples. The results show, both ABS and PLA performed well under the heat flow categories. While comparing to conventional manufacturing technologies, these 3D printed DMA results are showing some excellent results. These polymeric samples may prepare as composites and used for various applications, for better outcomes and capabilities. Storage modulus, while taking the temperature values of ABS to 90 °C maximum and for PLA about 48 °C. This will happen, but this pure form of materials printed through FDM also has such a very good energy storing capacity. Considering the loss modulus energy dissipation in the form of heat started from 110 °C, this is one of the good signs on the fabricated technique and build quality of ABS. The continues decrease in the degree of crystallinity of the PLA and ABS increases the meshing strength noted in the damping factor.

In this work, the effect of Inca peanut seed albumin fraction (IPA) on the rheological, thermal and microstructural properties of native corn starch (NCS) was firstly studied. Compared to the NCS, IPA addition could obviously decrease the transparency of NCS, and the transparency of NCS and NCS-IPA suspensions decreased during the storage time. The textural paraments of NCS pastes with or without IPA reached to the maximum at a concentration of 5%. Steady shear rheological tests showed that all systems were non-Newtonian fluid, and the consistency coefficient (K) values reached to the maximum at 5% IPA concentration. The storage and loss modulus values of NCS-IPA pastes were higher than those of NCS pastes, and curves of loss angle (tan δ) indicated that all pastes were typical weak gel. With the increasing addition of IPA, DSC analysis showed that the thermal properties (To, Tp and Tc) of NCS were significantly changed, whereas, there was no distinct difference in the enthalpy. Microscopy illustrated that there were some wrinkle shrinkage and severe folds on the NCS-IPA granules. Fourier-transform infrared (FT-IR) spectroscopy showed that the hydrogen bonding was primarily interaction forces between IPA and NCS molecules.

Acrylonitrile Butadiene Styrene (ABS) materials have been widely used in automotive and other manufacturing industries. To meet the specific requirements of industry the ABS materials are enhanced by adding fillers through compounding. Very few works are found for the improvement of viscoelastic and thermal characteristics of ABS material. This work is focused to prepare the thermoplastic composites of ABS with graphite filler and to analyze the dynamic mechanical, thermal and mechanical properties of composites. Thermoplastic composites were prepared with three different weight ratios (3, 6 and 9%) of graphite powder with ABS by employing a twin-screw extruder and the scanning electron microscopy (SEM) images confirmed the proper mixing of filler material with the matrix and the samples were prepared using injection molding machine. The viscoelastic properties of the composites were investigated through dynamic mechanical analysis (DMA) with three different frequencies of (0.5, 1 and 2) Hz and the DMA results indicate that the damping properties were significantly influenced by the presence of graphite particles in ABS. It was observed that the storage modulus (E’) is higher at the frequency of 2 Hz compared to the other two frequencies (0.5 and 1) Hz, but the loss modulus was almost the same at all three frequencies. The thermal stability and mass losses of the prepared samples, thermal gravimetric analysis (TGA) was performed and the TGA graphs showed the improvement in the thermal characteristics of neat ABS due to the addition of graphite filler. The DSC thermograms of neat ABS and ABS/graphite composites indicate that the glass transition temperatures of ABS/graphite composites were increased. The tensile strength increases up to 6 wt% of graphite and drastically drops at 9 wt% of the filler content. But the flexural strength of the ABS/graphite composites were reduced as the weight percentage of graphite content increases.

Hypothesis Relative to the bulk systems, the near-wall ( Experiments The combination of active microrheometry (multipole magnetic tweezers) and total internal reflection microscopy (TIRM) was employed to probe the structure–rheology relationships of microgel dispersions near a substrate surface. The ω, T, and ϕeff-dependences of the storage modulus (G′), loss modulus (G"), and softness (J) were analyzed by power-law and Arrhenius-like scaling theories. The fluctuation of J was further analyzed to give a quantitative description of the inhomogeneity in the near-wall regions. Findings (1) Remarkable differences in the rheological behaviors between the bulk and near-wall cases are revealed, where the latter shows a segmented overlap behavior in ϕeff; (2) Five regimes of ϕeff that correspond to distinct physical states of the microgel dispersions are determined; (3) The near-wall local structures exhibit more heterogeneity in the glass and colloidal gel regimes as compared to the liquid regime.

This work aimed to use natural deep eutectic solvents to modify the thermal, textural, freeze-thaw, and rheological properties of high amylose rice starch. Three different natural deep eutectic solvents (NADES) composed of sugar and organic acids were applied to modify the properties of starch dispersion. In presence of NADES, the onset temperature of starch was decreased, in comparison with starch in aqueous and glycerol medium. During thermal decomposition, starch with the aqueous and glycerol systems showed two-step weight losses whereas with NADES starch showed single-stage weight losses or decomposition. Moreover, negligible syneresis was observed for starch-NADES dispersion after 3rd cycle of the freeze-thaw process. The flow behavior of starch-NADES dispersion follows Herschel–Bulkley models as R2 (0.996 ≤ R2 ≤ 0.999) are higher than the Mizrahi-Berk model. The flow behavior index (n) of starch-NADES dispersion was closer to 1, indicated a nearly Newtonian fluid. The loss modulus (G″) value of starch-NADES dispersions was markedly higher than the corresponding storage modulus (G′) value and thus materials behaved like viscoelastic liquid. The present study manifested a green way to modify the properties of the high amylose starch to improve the processing stability.

Made available in DSpace on 2022-04-28T19:40:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-08-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Thermoplastic starch (TPS) is a widely studied biopolymer as an alternative to the use of conventional polymers. In this sense, the incorporation of fillers or reinforcements coming preferably from other substances of natural origin, can be an alternative to try to improve some mechanical and thermal properties of starch polymers. Thus, Kraft Lignin (KL), can be an excellent filler to be incorporated, since it presents mechanical and thermal properties and reduces the cost and weight of the final compounds. TPS films were prepared by casting using dimethyl sulfoxide (DMSO) as solvent and additives with 2, 4 and 8% KL. Characterization of TPS films and compositions with KL were carried out by Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), Dynamic Thermomechanical Analysis (DMTA), tensile testing and contact angle. Samples were also analyzed for biodegradation and for the ability to remove contaminants in water, Metil Orange (MO), by Ultraviolet-Visible Spectroscopy (UV–Vis). The FT-IR spectra of the films showed bands typical of functional groups derived from starch and lignin, with the intensity of these bands varying among the samples studied. Micrographs revealed slightly different morphologies among the films, but all showed irregular shapes with structures that appeared as plots. Increasing the percentage of KL led to an increase in contact angle values, showing a more hydrophobic behavior. In the TGA analysis, it was possible to observe a change in the main degradation event of the films for lower temperatures, especially of TPS – 4 and 8% KL compared to the TPS film. Films with KL had the peak of maximum degradation shifted to temperatures below the starch film, where the decrease in intensity of the main peak in the TPS - 4% KL and TPS - 8% KL samples demonstrates that there was less mass loss in the event. There was also in the percentage of residue as the addition of KL was increased The DMTA analyses allowed for the conclusion that presence of KL in TPS film allowed for an increase in its energy storage property, and that the loss modulus followed a decreasing order of storage modulus values to TPS - 8% KL from TPS. For the tensile strength property only TPS - 4% KL has significant improvement, and the elongation at break showed an increase for TPS – 4 and 8% KL compared to TPS. Samples showed a continuous and progressive biodegradation process, being completely biodegraded within 10 days. The monitoring of the ability to remove contaminants from water by UV–Vis, also showed promising results of compounds for this application. The best results were obtained, in most tests, for the TPS- 4% KL films. Polymers and Biopolymers Technology Laboratory (TecPBio) Institute of Science and Technology (ICT) Federal University of São Paulo (UNIFESP) Lignocellulosic Materials Laboratory Science and Technology Center for Sustainability (CCTS) Federal University of São Carlos (UFSCar), João Leme dos Santos, km 110 Science and Technology Institute of Sorocaba (ICTS) São Paulo State University (UNESP), Av. Três de Março, 511 Science and Technology Institute of Sorocaba (ICTS) São Paulo State University (UNESP), Av. Três de Março, 511 CAPES: 001 FAPESP: 2019/15976-0 FAPESP: 2019/19401-1 CNPq: 313989/2018-4

In this study, the effect of curing applied to jute woven fabric (four-layers) reinforced composite materials in which different proportions of acrylated epoxidized soybean oil (AESO) and epoxy resin are used as matrix material, on the thermal, thermo-mechanical and morphological properties of the composite materials are investigated. Composite material production is carried out by vacuum infusion method, whereas curing at 90 °C is done during production and post-curing at 120 °C is performed using a conditioning oven after production. Dynamic mechanical analysis (DMA) results show that the storage and loss modulus values of composite materials increase with increasing AESO ratio, while tan delta curves display that the bonds between the fiber and matrix of hybrid samples are stronger than composite materials using a single type of resin. This result is also supported by scanning electron microscope (SEM) images. The effect of curing (90 °C) and post-curing (120 °C) temperatures on the thermo-mechanical properties of the composite material is more clearly seen in epoxy composite samples whose glass transition temperature is higher than the room temperature. Besides, the decrease in glass transition temperature of the material with the increase in AESO content is obtained from both DMA and differential scanning calorimetry (DSC) plots.

Biodegradable poly(propylene carbonate) (PPC)/epoxidized soybean oil (ESO) blends with different component ratios were prepared by melt blending to improve the performance of PPC. The phase morphology, thermal properties, rheological properties and mechanical properties of the blends were investigated in detail. SEM examination revealed good interfacial adhesion between PPC matrix and ESO. According to DSC and DMA, as the content of ESO increased, the glass transition temperature of the PPC component increased, indicating that there was a strong interfacial interaction between the PPC matrix and ESO. The interfacial interaction may be caused by ring-opening reaction between the hydroxyl end groups of PPC and the epoxy groups of ESO, which restricted the chain movement of PPC matrix. The disappearance of the epoxy groups in FTIR indicated that the interfacial interaction between the two phases was due to the ring-opening reaction between PPC and ESO. With the addition of ESO, the thermal stabilities were enhanced. With the increasing ESO content, the modulus gradually decreased. However, the strength at yield, the strength at break and the elongation at break were increased for the PPC/ESO blends, suggesting that the enhancement of the strength and toughness of PPC was achieved by the incorporation of ESO. The rheological measurement revealed that the complex viscosity, storage modulus and loss modulus of PPC were increased with the increasing ESO content at low frequency, which indicated that the addition of ESO enhanced the melt strength of PPC instead of plasticizing PPC.

The dynamic rheological behavior of polypropylene (PP)/low-density polyethylene (LDPE) blending melts at 210 °C and 230 °C was measured by small-amplitude oscillatory shear mode on a rotational rheometer. The complex viscosity and dynamic modulus of pure PP are higher than those of pure LDPE at low frequency. For the blends with dispersion morphologies, Palierne model is applied to fit the storage modulus data and the model almost underestimates the data since most of the experimental dynamic modulus of the blends lay between that of pure PP and pure LDPE. While Lee and Park model predicts the dynamic storage data well for the PP/LDPE blends 90/10, 10/90 and 70/30 blends. For the 30/70 blend, this model describes the data much closer than Palierne model and a little deviation occurs at low frequency. The comparison between the two models’ fitting results indicates interaction among dispersed droplets should be considered.

Application of out-of-service rubber from a variety of sources is of both environment-protecting and resource-saving importance. To that end, recycled tire rubber was utilized as a filler to fabricate wood-high density polyethylene (HDPE) composite with enhanced toughening performance using the injection procedure in this work. Dosages of rubber powders were 0, 5, 10, and 15wt% based on the overall weight of poplar wood flour and HDPE (HDPE: wood flour = 70꞉30). The injection-fabricated composites were subjected to a four-cycle repetitive compressing loadings (0–3 kN) and dynamical mechanical analysis (DMA, room temperature to 150 ℃, in the dual cantilever mode). It was found that the rubber-filled materials exhibit advantageous energy absorption performance compared to wood-HDPE composites under repetitive compressions. The rubber-filled wood-HDPE composites are thermomechanically labile in an environment with raised temperature. The HDPE matrix substance occupies the predominant role in thermally yielding of the overall composite, typically in the temperature range of 50–75 ℃ resulting in a loss modulus peak. Up to 130–150 ℃, all the composites fully loses their moduli with loss factor (Tanδ) reaching its peak values of 0.30–0.38. To conclude, rubber-filled wood-HDPE is a qualified material applicable in proper temperature range.

The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations. Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed. Herein carbon black (CB) filled isoprene rubber (IR)/liquid isoprene rubber (LR) blend nanocomposites with similar crosslink density (ve) are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated. The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes. Meanwhile, tuning ve and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances. The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.

The present work investigating the effect of acetylation treatment on the plain woven banana fabric (PWBF) in a polyvinyl alcohol (PVA) matrix, which includes the banana fabric strength and fabric pull-out. This type of fabric treatment is normally used to improve the mechanical and thermo-mechanical behavior of composites. The raw PWBFs are treated with different acetylation percentages of concentrations (i.e., 2, 4, 6, 8, and 10) for 4 h at room temperature. The mechanical properties (i.e., tensile, flexural, and impact), thermo-mechanical behavior (i.e., storage modulus and loss modulus), surface morphology after tensile test, and water and biodegradability test of treated and untreated PWBF were investigated. The experimental results showed that the acetylation treatment was able to successfully remove hemicellulose, lignin, moisture content, waste impurities, and other unwanted particles from the PWBF surface and improve the mechanical and thermo-mechanical behavior of PWBF. In order to investigate PWBF/PVA internal bonding, the nature of fabric pull-out analysis was also carried out. It was found that the PWBF/PVA interfacial behavior increased after the acetylation treatment. The experimental results showed that treated composite was taken more time to complete biodegradable in natural soil and untreated composite specimen absorbed more water rate. In reality, the most favorable acetylation concentration was 6% in terms of maximum strength, a strong area of contact and bonding between PWBF/PVA, this is usually due to the reduction of hemicellulose, lignin, moisture content, impurities, and amorphous parts of the fabric.

The Untreated jute fiber reinforced composite (UTJFRC) and treated jute fiber reinforced composite (TJFRC) have been fabricated using compression molding processes. For chemical treatment of jute fiber mat sodium bicarbonate (NaHCO3) is used. The solution used for treatment has maintained pH of range 7–8 which show the ecofriendly treatment nature of sodium bicarbonate. Jute fiber mats were treated at three different concentration of sodium bicarbonate at 10, 20 and 30% for 4 h of treatment time. The prepared sample were characterized by dynamic mechanical thermal analysis (DMTA) and Izod impact test. All sample were cut according to ASTM standard to measure izod impact strength on impact tester. The composite sample which were treated at 10% concentration appear high impact strength. Even for dynamic mechanical properties treated jute fiber mat 20% concentration achieved maximum storage and loss modulus values. Even the glass transition temperature (Tg) is maximum shift for 20% concentration treated sample of jute/PLA composites. The improvement in properties because of good interfacial adhesion of jute and PLA achieved by sodium bicarbonate treatment of natural fiber.

Studies from the past two decades have demonstrated convincingly that cells are able to sense the mechanical properties of their surroundings. Cells make major decisions in response to this mechanosensation, including decisions regarding cell migration, proliferation, survival, and differentiation. The vast majority of these studies have focused on the cellular mechanoresponse to changing substrate stiffness (or elastic modulus) and have been conducted on purely elastic substrates. In contrast, most soft tissues in the human body exhibit viscoelastic behavior; that is, they generate responsive force proportional to both the magnitude and rate of strain. While several recent studies have demonstrated that viscous effects of an underlying substrate affect cellular mechanoresponse, there is not a straightforward experimental method to probe this, particularly for investigators with little background in biomaterial fabrication. In the current work, we demonstrate that polymers comprised of differing polydimethylsiloxane (PDMS) formulations can be generated that allow for control over both the strain-dependent storage modulus and the strain rate-dependent loss modulus. These substrates requires no background in biomaterial fabrication to fabricate, are shelf-stable, and exhibit repeatable mechanical properties. Here we demonstrate that these substrates are biocompatible and exhibit similar protein adsorption characteristics regardless of mechanical properties. Finally, we develop a set of empirical equations that predicts the storage and loss modulus for a given blend of PDMS formulations, allowing users to tailor substrate mechanical properties to their specific needs.

This paper highlights about the effect of modification of montmorillonite (MMT) clay with Benzalkonium chloride (BAC) on silk fibroin solution and film properties. MMT was modified by cation exchange method using BAC as the cation. BAC modified nanoclay was incorporated in silk fibroin by ultrasonication method for complete dispersive solution to form nanocomposite solution and films. Uniform dispersion of modified nanoclay in silk fibroin films was observed by FESEM-EDX analysis. Rheological studies of pure silk fibroin and nanocomposite solution showed that on adding the modified nanoclay, viscosity of silk fibroin solution decreases however, at higher loading concentration viscosity changes drastically. Dynamic viscoelasticity behavior analysis of nanocomposites showed a decrease in storage and loss modulus on comparison to pure silk fibroin solution. On adding the nanoclay, an increase in the loss factor was observed with an increase in frequency which indicates the dominancy of viscous behavior in nanocomposite solution. Addition of nanoclay in silk fibroin shows a prominent shift in heat flow observed in DSC analysis. Nanoclay induced the opacity in the nanocomposite films as pure silk fibroin films were more transparent. The electrical properties of nanocomposite films observed that at higher concentration of modified nanoclay showed a dynamic increase in the conductivity.

Starch and protein are common polymers in food, and their phase separation often occurs during food processing. Protein-fortified starch dough can be considered as a triple phase separation system, and the effect of phase separation on dough rheology warrants further research. In this study, starch doughs fortified with fish actomyosin were used, and their rheological properties were researched and explained with respect to phase separation. The results suggested that the phase separation of actomyosin-binder-starch granules in the raw dough affected the quality of dough. The addition of actomyosin significantly decreased stiffness and shear sensitivity but increased the fluidity of the blended dough. Moreover, it was found that the interaction between mung bean starch and actomyosin was very weak. The polymer molecules were connected by physical links. Owing to phase separation, it was presumed that “wall slip” occurred between the binder, starch granule, and actomyosin. The blended dough containing 30% of the added actomyosin (R3) showed the best recovery ability and the weakest molecular interaction (interaction type Z′ = 0.40 for storage modulus G′ and 0.31 for loss modulus G′′). Additionally, the phase structure of the model doughs was investigated. It was found that the starch network played a dominant role when 10% (R1) actomyosin was added. With the addition of actomyosin, the protein network formed gradually. A bicontinuous phase structure with interpenetrating network was observed in R3 (actomyosin = 30%). In summary, our findings demonstrate the feasibility to make blended doughs by mixing fish actomyosin and mung bean starch. Moreover, in terms of use in traditional noodle making, the blended R3 dough was found to be the best in terms of recovery ability and flow characteristics.

Agarose, a strongly gelling polysaccharide, is a common ingredient used to optimize the viscoelastic properties of a multitude of food products. Through aggregation of double helices via hydrogen bonds while cooling under quiescent conditions it forms firm and brittle gels. However, this behavior can be altered by manipulating the processing conditions viz shear. For example, gelation under shear leads to microgel particles with large surface area, which in turn leads to completely different rheological properties and texture. Such fluid gels are shown to play an important role in texture modification of foods and beverages for dysphagia patients. In this study, different concentration of agarose fluid gel (0.5 % wt, 1 % wt and 2 % wt) were considered. Rheological measurements of the microgel particles showed an increase of storage and loss modulus with increasing concentration. However, 1 % wt fluid gel exhibited the lowest viscosity in the low shear range and the shortest LVE range. Furthermore, the effect on the microstructure and size of gel particles were also investigated by using light microscopy and particle size analysis. It was observed that as the concentration of agarose increased the particle size and unordered chains present at the particle surface decreases. Based on our results, we propose specific models suggesting the impact of the particle size, the concentration and the “hairy” projections on the rheological and tribological properties that could help in understanding the differences in characteristics of fluid gels., Graphical abstract Image 1, Highlights • Formation of agarose fluid gels in dependence on concentration, temperature and shear rate. • Competing mechanism during gelation under shear of agarose fluid gels was studied. • The resulting gel particle structures, their size and shape vary with concentration. • Network structures, particle size and shape affect the rheological and tribological behavior. • Fluid gels provide unique properties of friction, viscosity and viscoelastic behavior.

Hydrogels are excellent soft materials to interface with biological systems. Precise control and tunability of dissipative properties of gels are particularly interesting in tissue engineering applications. In this work, we produced hydrogels with tunable dissipative properties by photopolymerizing a second polymer within a preformed cross-linked hydrogel network of poly(acrylamide). We explored second networks made with different structures and capacity to hydrogen bond with the first network, namely linear poly(acrylic acid) and branched poly(tannic acid). Gels incorporating a second network made with poly(tannic acid) exhibited excellent stiffness (0.35 ± 0.035 MPa) and toughness (1.64 ± 0.26 MJ m−3) compared to the poly(acrylic acid) counterparts. We also demonstrate a strategy to fabricate hydrogels where the dissipation (loss modulus) can be tuned independently from the elasticity (storage modulus) suitable for cell culture applications. We anticipate that this modular design approach for producing hydrogels will have applications in tailored substrates for cell culture studies and in load bearing tissue engineering applications.

This study aims at studying the dynamic mechanical and thermogravimetric properties of boron carbide (B4C) filled carbon fiber (CF)/epoxy composites (BC-CF/Ep composites) using the wet lay-up process assisted by vacuum bagging technique. The B4C fillers were used in varying filler weight percentages (1%, 3% and 5%) in the different CF/Ep composites and are uniformly mixed in epoxy system through ultrasonification process and was used as the matrix. The Toray make bidirectional twill (2 × 2) woven T800CF was used as the reinforcing material. The Dynamic Mechanical Analyzer (DMA) and Thermogravimetric Analysis (TGA) tests are conducted to study the dynamic capacity and thermal degradation behavior respectively. In the DMA, the storage modulus (E1), loss modulus (E11), damping behavior (Tanδ) and glass transition temperature (Tg) of CF/Ep composite specimens are studied with increasing temperature from (25–173)°C. The BC1% composites showed better storage modulus, loss modulus and damping factor, while unfilled CF/Ep and BC3% composites showed better Tg than other CF/Ep composites. As far as TGA is concerned, the BC1% composites exhibited better thermal stability than all other composites. The dynamic tests resulted in the trend of BC1% > unfilled CF/Ep > BC3% > BC5% composites. The TGA tests also followed the trend of BC1% > unfilled CF/Ep > BC3% > BC5% CF/Ep composites.

The physicochemical properties of corn starch (CS) and a component of granule shells (Cs) obtained through a granule shells separation process, were studied. The shells separation was accurately visualized and confirmed by SEM and TEM images. Both CS and Cs contained three components (amylopectin, intermediate fraction and amylose) with a Mw ranging from 4.11 × 107 to 11.42 × 107 g/mol. The amylose content of CS and Cs was in the following order: Cs-83 > CS > Cs-69 > Cs-76. There were no significant differences observed between CS and Cs-83 for the dynamic modulus, apparent viscosity, peak viscosity and final viscosity, while Cs-69 and Cs-76 exhibited a decreasing trend. The DSC results revealed that the transition temperatures of CS were significantly higher than those of Cs. There was an obvious decrease in the thermal degradation onset temperature (To) for the treated samples (CS:312.26 °C, Cs-69: 311.87 °C, Cs-76: 307.62 °C and Cs-83: 307.11 °C). The crystalline patterns of CS were converted from A-type to C-type during the granule shells separation process. The relative crystallinities of Cs were significantly lower than that of CS (26.87%). The FTIR results showed that intramolecular and intermolecular hydrogen-bonding (O H) of Cs were weakened after shells separation treatment.

Highly stable pine oil-loaded nanoemulsions were evaluated for nutraceutical and storage stability applications. Pine oil-loaded nanoemulsion preparation was done with pine oil as the oily phase and additionally with different ratios of the non-ionic surfactant (Tween 80) and cosurfactant (ethanol) in an aqueous solution using the isothermal low-energy or spontaneous emulsification method. A transparent and stable nanoemulsion was obtained with a combination of pine oil (5 wt %), surfactant mixture (35 wt %), and water quantity sufficient (qs) by the isothermal low-energy method. The mean droplet size and ζ-potential of the fabricated nanoemulsion were ≈14 nm and -3.4 mV, respectively. The size of the transparent nanoemulsion increased to ∼45 nm and showed turbidity at 60 °C. Microrheological investigation highlighted the gel-sol-gel conversion in the presence of applied angular frequency at 25 °C. The loss modulus shifted to lower frequency at 60 °C in comparison to other temperatures. The anticholinesterase (AChE) inhibition activity of the pine oil-loaded nanoemulsion suggested a possible therapeutic value, and at 0.10% concentration of the nanoemulsion, the AChE inhibition activity was ≈95.72 ± 5.59%. These studies have important implications in fabrication and optimization of a nanoemulsion as a delivery system for combating reminiscence in Alzheimer's disease and application in the nutraceutical-based industry. This isothermal low-energy method offers an advantage of preparing an edible oil delivery system using simple and rapid operational parameters.

Filled vulcanizates exhibit the nonlinear Payne effect under dynamic deformations at high strain amplitudes, while the underlining mechanisms are still in dispute. Herein, polydimethylsiloxane (PDMS) networks are prepared via end-linking of α,ω-vinyl-terminated PDMS chains by the thiol-ene reaction, and the influences of silica on the dynamic rheological responses are investigated. The presence of silica tends to improve the crosslinking density alongside reinforcing the network, while silica itself does not contribute to the loss factor markedly. Furthermore, silica could promote the onset strain amplitude of the Payne effect and manifest the very weak overshoot of loss modulus near the onset amplitude. By creating master curves of the Payne effect of the filled vulcanizates referenced to the end-linking networks, it is evidenced that this effect and the accompanied weak overshoot are mainly rooted in the nonlinear Rouse dynamics of the network strands.

The viscoelastic properties of semi-conductive UV cured urethane acrylate/silicon carbide nanocomposites (UV-PUA/SiC) containing 0.1, 0.3, 0.6, 1, 3, and 5% (wt) of SiC are studied. Scanning electron microscopy (SEM) was employed to examine the state of the spatial distribution of SiC particles in the matrix. In conjunction with the electron microscopy technique, dynamic mechanical thermal analysis (DMTA) was employed as an indirect tool for the microstructure characterization and evaluation of the network heterogeneity and cross-link density of the nanocomposites. The influence of SiC nanoparticles on the storage modulus, loss modulus, cross-link density, glass transition temperature, and activation energy for glass transition of the UV-PUA matrix are investigated. The effect of SiC content on the network structures and degree of curing of the nanocomposites was evaluated by William-Landel-Ferry (WLF) constants. The breadth of the glass transition in the tanδ curve and shape parameter (β) in the Kolrausch-Williams-Watts (KWW) equation were used to investigate the network heterogeneity of the samples. All these referred parameters increased with SiC nanoparticles loading up to 0.6% (wt). In contrast, upon introducing SiC at higher concentrations, the viscoelastic properties of the nanocomposites reduced significantly. SEM analysis was used to evaluate the DMTA results regarding the dispersion state of the nanoparticles in the matrix.

Red Balau saw dust was heat-treated at 180 °C and 200 °C for one hour and compounded with low-density polyethylene, LDPE, at 9, 20 and 37 wt%. The compounded materials were injection moulded into test specimens. Charpy impact assessment of the notched samples of the composites revealed that the peak load, P, and the critical stress intensity factor, Kc, increased with wood content and treatment temperature. While the energy to failure, W , and the critical strain energy release rate, Gc, decreased with wood content, the values were highest in composites made from wood flour treated at 180 °C and reduced in 200 °C treated wood composites. This behaviour revealed that heat treatment of wood flour at the 200 °C resulted in poorer impact properties of the composites. Dynamic mechanical analysis showed an increase in storage and loss modulus of composites made from untreated wood flour relative to the heat-treated ones. Tan delta values were also found to reduce in the heat-treated wood composites as a result of decreased damping. Heat treatment of wood flour at appropriate temperature enhanced both the mechanical and dynamic mechanical properties of the composites.

The discrete slip-link theory is a hierarchy of strongly connected models that have great success predicting the linear and nonlinear rheology of high-molecular-weight polymers. Three of the four parameters of the most-detailed model, which can be extracted from primitive-path analysis, give quantitative agreement with experimental data for all examined chemistries (polystyrene, polyisoprene, polybutadiene, and polyethylene). Here, we attempt to extract the remaining friction parameter from atomistic simulations. In particular, an available quantum chemistry-based force field for polyethylene oxide (PEO) was used to perform molecular-dynamics simulations of a 12 kDa melt. The Kuhn friction is obtained from the mean-squared displacement of the center-of-mass of the chains (MSD of COM) in the melt. The result is also corroborated using the relaxation modulus calculated through the Green–Kubo formula. Once the four parameters are determined for any chemistry, all parameters for all members of the slip-link hierarchy are determined. Then, using a coarser member of the hierarchy, the dynamic modulus of a 256 kDa PEO melt was predicted. The predictions are compared to experimental measurements performed at the same temperature. Unfortunately, the extracted friction is about 30% larger than the one observed in the experiment. However, two fundamentally different methods, one utilizing the MSD of COM and the other the relaxation modulus, gave consistent results for the extracted Kuhn friction. Therefore, the discrepancy presumably arises from insufficient accuracy in the force field. Nonetheless, the work demonstrates that theory predictions without adjustable parameters should be possible.

Since the silk fibroin is a precious material widely used in various fields, the discarded silk textile is a profound waste in resource-constrained settings. In this paper, with recyclability in mind, we selected waste silk from discarded silk quilt to make the regenerated silk fibroin (RSF) aqueous solutions. Mixing with water-soluble polyvinyl alcohol (PVA), the RSF/PVA blended solutions were made as a spinning dope for preparing the regenerated fibers. To optimize the parameters during the spinning process, we used the rheological measurement firstly to investigate the fundamental characters of solutions with various blending ratios and the effect of temperature on solutions. The results showed the RSF/PVA blended aqueous solutions were non-Newtonian fluids, and the apparent viscosity rose with the increasing PVA contents in co-solutions and decreased with the growth of the shear rate. The blending ratio had a certain influence on the viscoelasticity of co-solutions, the more the percentage of PVA, the higher the value of the viscoelasticity of co-solutions would be, and the co-solution with blending ratio of 6:4 (RSF:PVA) showed the greatest influence on storage modulus, while the solutions with more RSF exhibited more effect on loss modulus. Too much PVA content or too high RSF proportion in solutions was unfavorable to spinning. What’s more, the co-solutions with RSF content less than 40% had the most similar morphological structural systems, and the co-solutions containing more than 20% PVA had narrow distribution, linear and high molecular weight. For preventing protein denaturation, the temperature should not be higher than around 30 °C.

The time evolution of three-dimensional (3D) printed food structures as affected by their composition and postprinting stimulus is an area of research that has recently received increasing attention. In this study, the spontaneous shape change of 3D printed purple sweet potato purees of different formulations as triggered by microwave dehydration was investigated. The rheological properties, water distribution behavior, and dielectric properties of the purees were first studied. Addition of salt reduced the viscosity, storage modulus, loss modulus, and yield stress but increased the relaxation time of the purees. Addition of fructose syrup resulted in opposite results. Addition of both salt and syrup decreased the dielectric constant but increased the dielectric loss of the purees. Increased microwave power and salt content increased the rates of dehydration and deformation but decreased the maximum deformation degree of the printed samples. The syrup also decreased the maximum deformation degree. A desirable deformation pattern could also be achieved by manipulating the infill parameters. Transformation of two-dimensional planar flowers and butterflies into 3D configurations as a result of varying the aforementioned parameters is illustrated. The proposed technique to induce spontaneous shape change of a 3D printed starch-based product should lay a foundation for further application of four-dimensional food printing.

Polymer solution has been used for increasing viscosity of ophthalmic solution in order to prolong the retention of active drug in the eye. The ophthalmic solution must be sterilized, which may affect the rheology properties of viscosity-inducing polymers. The aim of this study was to investigate the effect of sterilization treatment on viscosity-inducing agents (i.e., poloxamer, polyvinyl alcohol; (PVA), methyl cellulose (MC), polyvinylpyrrolidone (PVP) and carbomer). The effect of membrane filtration and steam sterilization or autoclaving (121 °C, 15 Ib/inch2, 15 min) were determined. A rheometer was used to investigate the viscosity and viscoelastic properties between treated and untreated polymer solutions. The power law model, consistency index (k), and power law index (n) of polymer solution viscosity were compared. For viscoelastic properties, storage modulus and loss modulus were examined. The results demonstrated that, viscosity of carbomer and MC solution (1 and 2 %) were changed after steam sterilization. No difference in viscosity was observed for PVP, PVA and poloxamer solution, between untreated and treated samples. The storage and loss moduli of PVA solution after autoclaving were not different when comparing with the untreated polymer solution. From this study, it could be concluded that the sterilization treatment influenced the viscosity behavior and viscoelastic properties of polymer solution used as viscosity-inducing agent in ophthalmic solution. Therefore, the selection of polymer and sterilization method should be carefully considered.

Starches were isolated from three cultivars of red adzuki beans, including Da Hongpao (DHP), Bao Qinghong (BQH) and Zhen Zhuhong (ZZH), and their morphological, structural and physicochemical properties were studied. Statistical analysis of the physicochemical and functional properties data revealed a significant (P < 0.05) difference among the three starch types. Starch of DHP cultivar showed low amylose content, smooth and round particle morphology, with obvious polarised crosses. The average particle size of the three adzuki bean types was in the range of 35.58 43.29 ?m, with that of DHP being the smallest, 35.58 ?m. The X-ray diffraction patterns showed that all the starches were type A with reflections (2?) at 15.0°, 17.03° and 23.3°. The bands of Fourier transforms infrared spectra of the three starches revealed their carbohydrate properties, and the intensity of the Fourier spectral absorption band of starch from DHP was weaker than that of the other cultivars. Further, the relative crystallinity of the three starches ranged from 22.7 to 29.4%, and DHP showed the highest crystallinity of 29.4%. Additionally, starch of the DHP cultivar revealed high gelatinisation, peak viscosity and enthalpy as compared to those from the other two adzuki bean cultivars. The shear viscosity of the three starch types decreased with increasing shear rate; when the shear rate was 10 s-1, the shear viscosity of the DHP-derived starch significantly decreased. Moreover, both the modulus (G’) and the loss modulus (G’’) increased with increasing dynamic frequency, and the DHP-derived starch showed the lowest G’ and G’’ values. In summary, this work provides data that may help in promoting the application of starches isolated from red adzuki bean in the food industry.

Electric double layers (EDLs) are ionic structures formed on charged surfaces and play an important role in various biological and industrial processes. An extensive study in the past decade has revealed the structure of the EDL in concentrated electrolyte solutions of both ordinary salts and ionic liquids. However, how the EDL structure affects their material properties remains a challenging topic due to technical difficulties of these measurements at nanoscale. In this work, we report the first detailed characterization of the viscoelasticity of the EDL formed over a wide range of ion concentrations, including concentrated electrolyte solutions. Specifically, we investigate the complex shear modulus of the EDL by measuring the resonant frequency and the energy dissipation of a quartz crystal microbalance (QCM), a surface-sensitive device, immersed in aqueous solutions containing three types of solutes: an ionic liquid, 1-butyl-3-methylimidazolium chloride (BmimCl); an ordinary salt, sodium chloride (NaCl); and a nonelectrolyte, ethylene glycol (EG). For the two electrolyte solutions, we observe a monotonic decrease in the resonant frequency and a monotonic increase in the energy dissipation with increasing ion concentrations due to the presence of the EDL. The complex shear modulus of the EDL is estimated through a wave propagation model in which the density and shear modulus of the EDL decay exponentially toward those of the bulk solution. Our results show that both the storage and the loss modulus of the EDL increase rapidly with increasing ion concentrations in the low ion concentration regime (

Background Potato powder, a rich source of high-quality protein and starch, plays an important role in the production of functional foods. In this study, ball-mill processed potato powders with different particle sizes (278, 208, 129, and 62 μm) were analyzed in terms of physicochemical, pasting, rheological, and digestive properties. Results Scanning electron microscopy and laser diffraction analysis of the samples revealed mono-model particle-size distributions. X-ray diffraction analysis confirmed structure destruction of starch pellets. Proximate composition and physical property analysis showed an increase in the water, ash, protein, and starch content. Meanwhile, the water solubility index and swelling power values were found to increase with decreasing grain size, and so were the brightness (L*) and redness (b*) values of the potato powders. With particle size reduced to 129 μm, large changes were observed in gelatinization properties, such as peak viscosity, trough viscosity, breakdown viscosity, and final viscosity. Oscillatory rheology results also showed that, with the decrease in particle size, the storage modulus (G') and loss modulus (G″) improved, with highest storage modulus (G') observed in the 129 μm particle size. The hydrolysis rate and glycemic index also increased in the 129 μm potato powder. Conclusion The results provide information that could be useful for improving quality characteristics by using specific grain sizes in the development of potato-based products such as gluten-free products and ethnic food products with particular functional and rheological properties. © 2020 Society of Chemical Industry.

Asphalt-based composites have the ability to heal themselves.without the aid of external influences (energy supply or material supplement), the self-healing ability of asphalt mixture is quite limi...

This study investigated the impact of citric acid modification combined with alcoholic-alkaline treatment on physicochemical, textural and rheological properties of sorghum and corn starches. Both starches were modified with citric acid (CA) using concentrations (20 and 40%) w/w and were named as SCA and CCA, respectively. SEM analysis revealed that CA modified CWS (cold water-soluble) starches had cracks and more sharp edges as compared to their native counterparts. In FTIR spectra a new peak at 1730.50 cm−1 and 1733.12 cm−1 confirmed formation of distarch esters for SCA40 and CCA40. Increase in swelling power of CWS starches was observed after citric acid modification. Textural analysis showed that SCA20 and SCA40 formed smooth and soft gels suggesting reduced retrogradation tendency of these starches. The broader linear viscoelastic region of CCA40 and SCA40 indicated high shear resistance and well dispersed behavior of CWS citrates. Moreover, it was observed that all CWS starches showed increase in storage modulus (G′) and loss modulus (G″) values at higher frequencies indicating elastic behavior. CA modification conferred heat and shear stability to starches. This study provides the basic knowledge for the application of CA modified CWS starches in many instant, refrigerated and frozen food products.

Incompatibility of chitin nanomaterials with organic solvents is challenging in the design of the desirable organogels. The long hydrocarbon chains were covalently grafted on the surface of nanochitins, with the attachment of reactive allyl groups and improved dispersion in organic solvents. The reactive thiol groups of poly (ethylene glycol) were introduced into the allyl-nanochitin suspensions to produce the organogels by the thiol-ene click reaction. Attributed to the UV-induced cross-linking between the soft segments of thiolated−PEG and the allyl-nanochitin, the stable organogels with the storage modulus higher than the loss modulus by one order of magnitude were obtained, exhibiting the significant phase transition and mechanical enhancement on the rheological behavior. The combination of crystalline allyl-nanochitin and polymeric chains played a crucial role in the construction of the micro-network, attributing to the stability and mechanical strength of the organogels.

This study aimed to determine the physicochemical and rheological characterization of Rocket seed gum (RSG) as a plant-based natural gum. Moisture, ash, protein, monosaccharide composition, and pH value were determined. Mannose and galactose were the main monosaccharides with a ratio of (mannose/galactose) 1.52. The absorptions at wavenumber 2855 cm-1 and 2922 cm-1 indicate the presence of galactose and arabinose. RSG showed shear-thinning flow behavior at all concentrations. The K value of the RSG ranged between 0.24 and 6.31 Pa.sn and significantly increased with increased gum concentration. Hysteresis area was found 11.53-183.23 and increased with increasing gum concentration. The percentage recovery for the G′ was significantly affected by gum concentrations and found as 42.54-81.20. RSG showed a solid-like structure, the storage modulus (G′) was higher than the loss modulus (G′′) in all frequency range. G′ and G′′ value increased with increased RSG concentration. The physicochemical and rheological characterization indicated that RSG could be evaluated as thickeners and gelling agents in the food industry.

Hydrocolloid-based films are a good alternative in the development of biodegradable films due to their properties, such as non-toxicity, functionality, and biodegradability, among others. In this work, films based on hydrocolloids (gellan gum, carrageenan, and guar gum) were formulated, evaluating their dynamic rheological behavior and creep and recovery. Maxwell’s classical and fractional rheological models were implemented to describe its viscoelastic behavior, using the Vortex Search Algorithm for the estimation of the parameters. The hydrocolloid-based films showed a viscoelastic behavior, where the behavior of the storage modulus (G′) and loss modulus (G″) indicated a greater elastic behavior (G′&gt, G″). The Maxwell fractional model with two spring-pots showed an optimal fit of the experimental data of storage modulus (G′) and loss modulus (G″) and a creep compliance (J) (Fmin&lt, 0.1 and R2&gt, 0.98). This shows that fractional models are an excellent alternative for describing the dynamic rheological behavior and creep recovery of films. These results show the importance of estimating parameters that allow for the dynamic rheological and creep behaviors of hydrocolloid-based films for applications in the design of active films because they allow us to understand their behavior from a rheological point of view, which can contribute to the design and improvement of products such as food coatings, food packaging, or other applications containing biopolymers.

Fused Deposition Modeling (FDM) is a widely used additive manufacturing (AM) process due to simple operation, relatively low cost and wide range of available material options. Commonly used feedstock materials in FDM are petroleum-based polymers. These polymers significantly influence the environment in terms of CO2 and plastic waste addition. To minimize these effects, understanding the bio-based and biodegradable polymers for engineering applications are essential. PolyLactic Acid (PLA) is a bio-based, biodegradable, biocompatible and recyclable thermoplastic polymer used in engineering and medical application. Dynamic Mechanical Analysis (DMA) is an experimental technique used to analyze the polymers’ viscoelastic behaviour with varied temperature, frequency, and stress/strain. Post-processing heat treatment processes, including annealing, can influence mechanical properties of the processed polymer parts. Improved crystallinity, Heat Deflection Temperature (HDT) and increased glass transition temperature (Tg) are a few advantages of annealing thermoplastic polymers. Annealing process parameters like temperature, time, and cooling rates can significantly affect the various mechanical properties gained through the annealing process. The dynamic mechanical properties, such as storage modulus, loss modulus, and damping factor, are also affected by annealing. The effect of annealing parameters on dynamic mechanical properties of FDM printed PLA is studied and reported.

Poly(vinyl alcohol) (PVA) in multifilament and braided yarns (BY) forms presents great potential for the design of numerous applications. However, such solutions fail to accomplish their requirements if the chemical and thermomechanical behaviour is not sufficiently known. Hence, a comprehensive characterisation of PVA multifilament and three BY architectures (6, 8, and 10 yarns) was performed involving the application of several techniques to evaluate the morphological, chem- ical, thermal, and mechanical features of those structures. Scanning electron microscopy (SEM) was used to reveal structural and morphological information. Differential thermal analysis (DTA) pointed out the glass transition temperature of PVA at 76 °C and the corresponding crystalline melt- ing point at 210 °C. PVA BY exhibited higher tensile strength under monotonic quasi-static loading in comparison to their multifilament forms. Creep tests demonstrated that 6BY structures present the most deformable behaviour, while 8BY structures are the least deformable. Relaxation tests showed that 8BY architecture presents a more expressive variation of tensile stress, while 10BY of- fered the least. Dynamic mechanical analysis (DMA) revealed storage and loss moduli curves with similar transition peaks for the tested structures, except for the 10BY. Storage modulus is always four to six times higher than the loss modulus., This work was funded by European Regional Development funds (FEDER) through the Competitiveness and Internationalization Operational Program (POCI)—COMPETE andby Na-tional Funds through Portuguese Fundação para a Ciência e Tecnologia (FCT) under the project UID/EMS/50022/2020, UID/EEA/04436/2019 andUID/ CTM/00264/2019. Andrea Zille acknowledges financial support of the FCT through the project PTDC/CTM-TEX/28295/2017,and Nuno Dourado acknowledges financial support of the FCT through the project PTDC/EME-SIS/28225/2017. M.F.S.M. de Moura acknowledges the ‘Laboratório Associado de Energia, Transportes e Aeronáutica’ (LAETA) for the financial support.

This work aims at understanding the influence of the substrate temperature (Ts) on the viscoelastic properties of propanethiol plasma polymer films (PPFs). By means of state-of-the-art AFM characterization-based techniques including peak force quantitative nanomechanical mapping (PFQNM), nano dynamic mechanical analysis (nDMA) and "scratch" experiments, it has been demonstrated that the mechanical behaviour of PPFs is dramatically affected by the thermal conditions of the substrate. Indeed, the material behaves from a high viscous liquid (i.e. viscosity ∼ 106 Pa s) to a viscoelastic solid (loss modulus ∼ 1.17 GPa, storage modulus ∼ 1.61 GPa) and finally to an elastic solid (loss modulus ∼ 1.95 GPa, storage modulus ∼ 8.51 GPa) when increasing Ts from 10 to 45 °C. This behaviour is ascribed to an increase in the surface glass transition temperature of the polymeric network. The latter has been correlated with the chemical composition through the presence of unbound molecules acting as plasticizers and the cross-linking density of the layers. In a second step, this knowledge is exploited for the fabrication of a nanopattern by generating surface instabilities in the propanethiol PPF/Al bilayer system.

Sulfate erosion is a major cause of concrete durability deteriorations, especially for the service tunnels which are in sulfate erosion for a long time. Accurately predicting the concrete damage failure under sulfate erosion has been a challenging problem in the evaluation and maintenance of concrete structures. Here we design the dry-wet cycle test of service tunnel concrete under sulfate erosion, and analyze the Elastic relative dynamic modulus(Erd) and mass under 35 times cycle periods. Then we develop an autoregressive integrated moving average (ARIMA) prediction model linking damage failure to Erd and mass. The results show that the deterioration of concrete first increased and then decreased with an extension of the dry–wet cycle period. Moreover, based on a finite set of training data, the proposed prediction approach shows high accuracy for the changes of concrete damage failure parameters in or out of the training dataset. The ARIMA method is proven to be feasible and efficient for predicting the concrete damage failure of service tunnel under sulfate erosion for a long time.

In this study, the effects of the addition of pectin (PEC) on the physicochemical properties and freeze-thaw stability of waxy rice starch (WRS) were investigated. As PEC content increased, the pasting viscosity and pasting temperature of WRS significantly increased (p &lt, 0.05), whereas its breakdown value and setback value decreased. Differential scanning calorimetry showed that the addition of PEC increased the gelatinization temperature of WRS, but decreased its gelatinization enthalpy. Rheological measurements indicated that the addition of PEC did not change the shear-thinning behavior of WRS–PEC blends, and the storage modulus and loss modulus were positively correlated with PEC content. Moreover, the textural parameter of WRS decreased with the increase in PEC content. Furthermore, the addition of PEC decreased the transmittance of starch paste, but enhanced the freeze-thaw stability of WRS to some extent. These results may contribute to the development of WRS-based food products.

In this work, the effects of alkaline treatment and hybridization on the thermal properties of sugar palm yarn/glass fiber were investigated. The sugar palm fiber was treated with 1% of sodium hydroxide (NaOH) solution for 1 h and the ratio of between matrix and reinforcement was 70/30 wt.% and 60/40 wt.%, respectively, while the ratio of reinforcement between sugar palm yarn fiber and glass fiber was 70/30 wt.%, 60/40 wt.% and 50/50 wt.%, respectively. The thermal properties of the hybrid composites were analyzed using a dynamic mechanical analyzer (DMA) and Thermogravimetric analysis (TGA). The storage modulus (E'), loss modulus (E'') and damping factor (tan δ) were evaluated as a function of the alkaline treatment and different percentages of fiber loading. Also, the peak high was investigated for the tan δ curves. In the glassy state area, a higher glass fiber loading hybridized with treated sugar palm fiber exhibited the highest storage modulus, loss modulus and the lowest damping factor. TGA demonstrated that the percentage of residue decreased as the glass fiber loading increased. Overall, the hybridization of glass fiber with treated sugar palm fiber enhances the thermal properties of the hybrid composites for structural applications. Keywords: Sugar palm fiber, Glass fiber, Yarn, DMA, TGA, Alkaline treatment, Unsaturated polyester

Globally around 300 million tonnes of plastic are produced, of which, less than 10% is recycled. Implementing recycled plastics in manufacturing i.e., by reusing them helps in the reduction of waste plastic scrap eventually. In this paper, an experimental study on recycled Polypropylene (RPP) and recycled High-Density Polyethylene (RHDPE) is carried out. The mechanical properties of the materials such as tensile strength, hardness, Young’s modulus, Impact strength, heat deflection temperature are evaluated using ASTM standards and further, the results are compared with the virgin Polypropylene & High-Density Polyethylene. Dynamic mechanical analysis is also performed on the samples to study the storage modulus, loss modulus, and tan delta values. In the investigations performed, it is observed that the Recycled materials have a lesser tensile strength, impact resistance, hardness when compared to the virgin materials. However, RHDPE has shown fairly good results when compared to RPP in impact resistance and tensile strength hence can be used in construction, military, and industrial applications. On the other hand, RPP has shown good results in terms of Hardness and Young’s Modulus, hence can be utilized in aircraft, automotive and engineering applications.

An attempt has been made in the present work to develop hybrid blended composites using epoxy resin (PETEP) derived from waste polyethylene terephthalate (PET) bottles and bio-phenolic (cardanol)-based benzoxazine (CBz) reinforced with functionalized bio-carbon (f-PJC) obtained from Prosopis juliflora (PJ) for high performance applications. The molecular structure, thermal properties, thermo-mechanical behaviour, morphology, surface properties, and corrosion resistance of the composites were studied by different analytical methods, and the obtained results are reported. Dynamic mechanical properties such as the storage modulus (2.591 GPa), loss modulus (1.299 GPa) and cross-linking density (5.1 × 107 J mol−1 K−1) were improved in the case of the 5 wt% f-PJC/PETEP–CBz composite compared to those of the PETEP–CBz blended matrix and the f-PJC/PETEP–CBz composites with other weight percentages. Among the studied bio-carbon-reinforced hybrid composites with different weight percentages, the 5 wt% f-PJC/PETEP–CBz composite shows a higher value of char yield (38.37%), with an enhanced glass transition temperature of 285 °C and an improved water contact angle of 111.3°. Results obtained from corrosion studies infer that these hybrid composites exhibit improved corrosion resistance behaviour and effectively protect the surface of mild steel specimens from corrosion. It is concluded that the present work can be considered as an effective method for utilizing waste products and sustainable bio-materials for the development of high performance value-added hybrid composites for thermal and corrosion protection applications.

Soft contacts present different tribological responses compared to stiff materials, especially when soft materials exhibit viscoelastic behaviour, as viscoelastic materials have intermediate mechanical properties between viscous liquids and elastic solids. In this work, we investigated the influence of viscoelasticity of soft materials on sliding friction in dry and lubricated conditions. To achieve this, soft tribopairs with varying viscoelasticity were obtained by tuning the weight ratios of polydimethylsiloxane (PDMS) base and curing agent. The real-time friction force and preload were observed over multiple conditions, with systematic control of lubricant viscosity, preload, and sliding velocity. Tribopairs with a higher proportion of viscous character had more oscilliations in the friction force. They also presented a higher friction coefficient due to the increased contribution of viscoelastic hysteresis losses on friction. Through regression analysis, the models of the friction coefficient were found, which are in good agreement with experimental results. From the models, we found that in both dry and lubricated conditions, viscoelasticity of tribopairs, indicated as the loss modulus or loss tangent, plays a key role in determining the friction coefficient. This influence is particularly significant for dry contacts due to the direct interactions between surfaces of tribopairs. This study provides empirical proof and a focused analysis on the role of viscoelasticity in tribological contacts.